Not only this post in the forum, theymos explains more about his approach for the forum in Reddit. The forum is a centralized one, but admin has core approach to keep it as a free place to discuss for all, at least with some minimum restrictions and systems, to minimize spamming and scamming. Theymos admits that things become more complicated when bitcointalk.org become bigger over years, and it is hard to satisfy all users in the forum. However, he will keep giving people free rights to express their ideas, just under minimum rules and restrictions. If they don't agree with rules, or agree then violate rules, they should leave the forum and will be punished with some sort of punishments (temp / perm / signature bans)
Primarily, it's just that freedom + size = mess, and with bitcointalk.org I've chosen to keep freedom about as high as possible, for example allowing paid signature ads, poor English, micro-earning services which often attract a spammy crowd, etc. Banning these things (and other noise-generating factors) would be easily possible, and would immediately lead to a cleaner environment, but it'd also be a less free environment. IMO there are enough highly-controlled platforms around, and I'd prefer to try maximizing the freedom axis. (Maximizing freedom on the forum was a policy started by Satoshi when he was an admin, BTW, though it was years after he left before the forum became large enough for freedom to actually come in conflict with signal much.)
Bitcointalk.org is under active development on two parallel paths:
First, although the outward appearance hasn't changed much at all since 2010, I have made tons of changes to the code, including many features. About a year ago for example I added the Merit system, which has improved signal-to-noise quite a bit, by means of changing incentives.
Second, a completely new software platform has long been in development. This software is open source, can be run now, and an instance of it is available for example at
https://www.cryptos-currencies.com/ . But I don't think that it's quite complete enough to migrate bitcointalk.org to it yet.
On both development paths, we try to tackle signal-vs-noise by methods such as categorizing posts better, improving incentives, trying to create smaller sub-communities, etc., but not via restriction, if at all possible.
While I don't claim to have nearly maximized the signal-to-noise which might be possible even given a high degree of freedom, bitcointalk.org is pretty anarchic, and it will always be so. (Though note that some sections are much better than others.) If that doesn't appeal to you, then you should use a different site. Smaller communities, like IRC channels and similar, can be both free and have a high signal-to-noise ratio. This was bitcointalk.org in 2010-2013, but it's now too large. You can also have large communities that are more strictly moderated, like /r/Bitcoin.